Method of lining an inner surface of a tubular and system for doing same

ABSTRACT

A method of lining an inner surface of a tubular with a polymer, includes positioning a polymer injecting head within the tubular, forming an annular space between the injecting head and an inner surface of the tubular, injecting polymer through the injecting head into the annular space, and moving the polymer injecting head longitudinally relative to the tubular while injecting polymer.

BACKGROUND

Typically applying a polymeric layer to the inner surface of a tubular,such as a stator for a mud motor for example, involves attaching a moldwithin the tubular thereby defining a cavity between the mold and asurface of the tubular. The polymer is injected through the mold andinto the cavity. For tubulars that are long and have small inner radialdimensions it can be difficult to inject the polymer to fully fill thecavity. In applications wherein the polymer is viscous while injectingthe difficulty of filling the cavity is exacerbated. As such, those thatpractice in the art of applying such layers are always receptive tosystems and methods that alleviate the foregoing difficulties.

BRIEF DESCRIPTION

Disclosed herein is a method of lining an inner surface of a tubularwith a polymer. The method includes, positioning a polymer injectinghead within the tubular, forming an annular space between the injectinghead and an inner surface of the tubular, injecting polymer through theinjecting head into the annular space, and moving the polymer injectinghead longitudinally relative to the tubular while injecting polymer.

Also disclosed is a system for lining an inner surface of a tubular. Thesystem includes, an injecting head having at least one nozzle configuredto inject a polymer therethrough into an annular space defined betweenthe injecting head and an inner surface of the tubular. The system isconfigured to move the injecting head relative to the tubular while theinjecting head is injecting polymer through the at least one nozzle toleave a layer of the polymer a full 360 degrees against the innersurface of the tubular.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 depicts a cross sectional view of a system for lining an innersurface of a tubular;

FIG. 2 depicts a cross sectional view of the system of FIG. 1 taken atarrows 2-2;

FIG. 3 depicts a partial cross sectional perspective view of a polymerand tubular assembly created with the system of FIG. 1; and

FIG. 4 depicts a cross sectional view of an alternate embodiment of asystem for lining an inner surface of a tubular disclosed herein.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

Referring to FIGS. 1 and 2, an embodiment of a system for lining aninner surface of a tubular is illustrated at 10. The system 10 includes,an injecting head 14 having body 16 with at least one nozzle 18 with sixof the nozzles 18 being illustrated in this embodiment. The system 10 isconfigured to inject polymer 22 through the injecting head 14 andthrough the nozzles 18 into an annular space 26 defined between theinjecting head 14 and an inner surface 30 of a tubular 34 that is beinglined. The injecting head 14 is longitudinally movable in the directionof arrow A (in FIG. 1) relative to the tubular 34 while the polymer 22is being injected. A portion 38 of the polymer 22 is able to at leastpartially set or partially solidify before a tail 42 of the injectinghead 14 is moved away from the portion 38. As such, an inner surface 46of the polymer 22 is contoured to have a profile 50 defined by an outersurface 54 of the injecting head 14.

In the illustrated embodiment the system includes a temperature alteringhead 58 that is integrated into the tail 42 of the injecting head 14.The temperature altering head 58 can include a heater or a cooler toalter the temperature of the head 58. One use of the temperaturealtering head 58 is to vulcanize or cure the polymer 22. A goodcandidate for usage as the polymer in such instance would be a rubber.The system 10 in this embodiment is configured so that the vulcanizationof the polymer 22 is completed by the heating of the heads 14 and 58 sothat no additional heating is required after the heads 14, 58 have beenwithdrawn from the tubular 34. In so doing the vulcanizing is donesequentially as the heads 14, 58 are moved longitudinally relative tothe polymer 22. Additionally, the tail 42 can be tapered so that it haslarger radial dimensions at points further from the nozzles 18. This canallow the tail 42 to exert increases in pressure to the polymer 22during the vulcanizing process.

In addition to longitudinally moving the injecting head 14 relative tothe tubular 34 while the polymer 22 is being injected, the injectinghead 14 may be rotated. In embodiments wherein the outer surface 54 ofthe injecting head 14 is none circular, such as one having lobes 62 asshown in FIG. 2, the combination of longitudinal and rotational movementof the injecting head 14 will cause the profile 50 in the inner surface46 of the polymer 22 to have one or more helical channels 66. Thishelical channeled profile 50 is best seen in the partial cross sectionalperspective view of FIG. 3 that shows a cured portion of the polymer 22within the tubular 34. The assembly formed by the polymer 22 and thetubular 34 can be a stator for a mud motor, for example, as are used indownhole industries such as the hydrocarbon recovery and the carbondioxide sequestration industries. In a mud motor application the tubular34 and the polymer 22 with the helical channel 66 formed therein canserve as a stator assembly. Stator assemblies are often very longcompared to their radial dimensions. Employing the system 10 disclosedherein allows an operator to consistently and repeatedly apply thepolymer 22 to very long tubulars 34, unlike processes that requireassembling a mold core within the tubular 34 and trying to injectviscous polymer to fill the cavity defined between the core and a longtubular. Such processes suffer from mold fill problems related to theshot size, the long distance runs the polymer must travel through thecore before reaching the cavity, and the slow flow rates associated withhigh viscosity of the polymers being injected.

The system 10 can also include optional features to improve its functionfurther. For example, a lubricant 70 such a mold release agent can beapplied between the polymer 22 and the injecting head 14 through porting74 in the injecting head 14. Injecting the lubricant 70 can decreasefriction associated with moving the injecting head 14 relative to thestationary polymer 22. Any practical number of outlets from the porting74 can be provided to facilitate injection of the lubricant 70 a full360 degrees around the injecting head 14 similar to the manner in whichthe nozzles 18 inject the polymer 22 a full 360 degrees around theinjecting head 14.

Similarly, a plurality of passageways 78 can optionally be incorporatedin the injecting head 14 to apply adhesive 82 to the inner surface 30 ofthe tubular 34 just prior to the polymer 22 being injected thereagainst.The adhesive 82 can be used to improve bonding between the polymer 22and the tubular 34.

An additional optional temperature altering member 86 is also shown inFIG. 1. The temperature altering member 86 is positionable outside ofthe tubular 34 and is configured to alter the temperature of the polymer22 in a manner similar to that of temperature altering head 58. As suchthe member 86 can work in unison with the head 58 or separately.Regardless of whether the member 86 acts alone or with the head 58,configuring it to move relative to the tubular 34 and thus the polymer22 allows it to be smaller than the full length of the polymer 22 whilebeing able to alter the temperature of the complete polymer 22 whenaltering properties of the polymer 22 such as through vulcanization, forexample.

Unlike conventional systems wherein a mold must be sized to fit eachtubular to be coated, a single one of the systems 10 disclosed hereincan be used to coat tubulars 34 of various lengths. Additionally, thissize matching requirement of molds of conventional systems means theoverall size (length primarily) of the tool is greater, possibly muchgreater than the size of the system 10 disclosed herein that can coatthe same tubulars. The smaller size and use of just one of the systems10 for various sized tubulars can result in significant savings in costof fabrication, materials, manpower and inventory over conventionalsystems.

Referring to FIG. 4, an alternate embodiment of a system for lining aninner surface of a tubular is illustrated at 110. The system 110 differsfrom the system 10 primarily in that the shape of an inner surface 130of tubular 134 has a helical contour with channels 140 (similar infashion to the inner surface 46), in contrast to the inner surface 30 ofthe tubular 34 of system 10 that is cylindrical. Since the contouredouter surface 54 of the injecting head 14 is complementary to the innersurface 130 a radial dimension 136 of the polymer 22 remainssubstantially constant. The system 110 requires coordination of movementof the injecting head 14 in both the longitudinal and rotationaldirections while injecting the polymer 22 to assure that the lobes 62remain properly aligned with the channels 140 as the polymer 22 isinjected against the inner surface 130.

While the invention has been described with reference to an exemplaryembodiment or embodiments, it will be understood by those skilled in theart that various changes may be made and equivalents may be substitutedfor elements thereof without departing from the scope of the invention.In addition, many modifications may be made to adapt a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof. Therefore, it is intendedthat the invention not be limited to the particular embodiment disclosedas the best mode contemplated for carrying out this invention, but thatthe invention will include all embodiments falling within the scope ofthe claims. Also, in the drawings and the description, there have beendisclosed exemplary embodiments of the invention and, although specificterms may have been employed, they are unless otherwise stated used in ageneric and descriptive sense only and not for purposes of limitation,the scope of the invention therefore not being so limited. Moreover, theuse of the terms first, second, etc. do not denote any order orimportance, but rather the terms first, second, etc. are used todistinguish one element from another. Furthermore, the use of the termsa, an, etc. do not denote a limitation of quantity, but rather denotethe presence of at least one of the referenced item.

What is claimed is:
 1. A method of lining an inner surface of a tubularwith a polymer, comprising: positioning a polymer injecting head withinthe tubular; forming an annular space between the injecting head and aninner surface of the tubular; injecting polymer through the injectinghead into the annular space; moving the polymer injecting headlongitudinally relative to the tubular while injecting polymer; andforming a helical shaped channel on an inner surface of the polymer. 2.The method of lining an inner surface of a tubular with a polymer ofclaim 1, further comprising vulcanizing the polymer.
 3. The method oflining an inner surface of a tubular with a polymer of claim 2, furthercomprising vulcanizing the polymer sequentially from one end of thetubular to the other.
 4. The method of lining an inner surface of atubular with a polymer of claim 1, further comprising moving atemperature altering head with the polymer injecting head and alteringtemperature of the injected polymer with the temperature altering head.5. The method of lining an inner surface of a tubular with a polymer ofclaim 1, further comprising rotating the polymer injecting head relativeto the tubular while it is moving longitudinally.
 6. The method oflining an inner surface of a tubular with a polymer of claim 1, furthercomprising maintaining a substantially constant radial dimension of thepolymer.
 7. The method of lining an inner surface of a tubular with apolymer of claim 1, further comprising injecting the polymer tocontinuously cover 360 degrees of the inner surface of the tubular. 8.The method of lining an inner surface of a tubular with a polymer ofclaim 1, further comprising bonding the polymer to the inner surface ofthe tubular.
 9. A method of lining an inner surface of a tubular with apolymer, comprising: positioning a polymer injecting head within thetubular; forming an annular space between the injecting head and aninner surface of the tubular; injecting polymer through the injectinghead into the annular space; and moving the polymer injecting headlongitudinally relative to the tubular while injecting polymer furthercomprising injecting adhesive between the polymer and the tubular.
 10. Amethod of lining an inner surface of a tubular with a polymercomprising: positioning a polymer injecting head within the tubular;forming an annular space between the injecting head and an inner surfaceof the tubular; injecting polymer through the injecting head into theannular space; and moving the polymer injecting head longitudinallyrelative to the tubular while injecting polymer further comprisinginjecting a lubricant between the polymer and the polymer injectinghead.
 11. A method of lining an inner surface of a tubular with apolymer comprising: positioning a polymer injecting head within thetubular; forming an annular space between the injecting head and aninner surface of the tubular; injecting polymer through the injectinghead into the annular space; and moving the polymer injecting headlongitudinally relative to the tubular while injecting polymer furthercomprising solidifying portions of the polymer before the polymerinjecting head is moved out of contact with the solidified portions ofthe polymer.